The present disclosure generally relates to devices and methods for facilitating proper placement of a medical prosthesis relative to a patient's anatomical structures. More particularly, the present disclosure relates to a medical prosthesis including markers that facilitate placement of the medical prosthesis relative to the patient's anatomical structures.
Heart failure is defined as the inability of the heart to pump enough blood to sustain normal bodily functions. Heart failure may be associated with a mechanical failure of a native valve. Such failures may arise because of congenital defects or as a result of age-related changes, infections, or other conditions.
Mechanical failures of the heart may result from a valve disorder. The heart has four valves: the tricuspid, pulmonary, mitral, and aortic valves. These valves have tissue flaps that open and close with each heartbeat. The flaps ensure proper blood flow through the four chambers of the heart and to the rest of the body. The heart valves sometimes have the following types of disorders: regurgitation, stenosis, and atresia.
Regurgitation (backflow through or around a valve) often occurs when the valve does not close tightly enough, thereby resulting in blood leaking back into the chambers of the heart rather than flowing forward through the heart or into arteries. Regurgitation often occurs because of prolapse, i.e., when the cusps or leaflets of the valve bulge back into an upper heart chamber during diastole. Stenosis occurs when the cusps or leaflets of a valve stiffen or fuse together, thereby preventing the valve from fully opening and inhibiting sufficient blood flow through the valve. Atresia occurs when a heart valve lacks an opening for blood to pass through.
Heart valve repair or replacement surgery restores or replaces a defective heart valve. The implantation of prosthetic cardiac valves has become increasingly common. One such procedure known as Transcatheter Aortic Valve Implantation (TAVI) uses a prosthetic valve mounted on a stent that displaces the diseased native aortic valve. The prosthetic valve is delivered by compressing it to approximately the width of a pencil and introducing it through a variety of access approaches including a transfemoral, transapical, transaortic, subclavian, or radial approach. Using ultrasound and X-ray guidance, the device is positioned and deployed at the level of the aortic annulus. As the device expands, it is anchored onto and displaces the diseased native valve to restore normal blood flow.
The replacement or repair of the aortic valve with a prosthetic device presents several challenges, including assessing the size and shape of the aortic annulus prior to implantation of the prosthetic device. Selecting an appropriately sized and shaped prosthetic device may pose several challenges because different techniques for measuring the aortic annulus may provide different measurements and measuring during systole or diastole may also have implications for sizing.
Even when an appropriately sized and shaped prosthetic device is selected, precise placement of the device is challenging. Since valves are often made from material that is not radiopaque, such as tissue or fabric, radiologic imaging techniques do not provide a direct way of determining the location of important regions of the valve. The stent typically is metallic and can be visualized in an x-ray image such as a fluoroscopic image. However, even if a clinician possesses a high degree of knowledge as to the construction of the valve assembly, e.g., the placement of the valve with respect to the stent, various regions of the valve assembly may appear to be the same or substantially the same when viewed using radiologic imaging techniques. Due to these challenges, the clinician often finds it difficult to guide the valve to the desired position relative to the patient's vasculature.
Appropriate placement and fit of the valve with respect to a patient's vasculature is important in ensuring proper functioning of the device. An improper fit or placement of the device may result in incomplete apposition or contact with the native aortic annulus, which may cause complications such as perivalvular leakage.
Therefore, a continuing need exists for devices and methods that facilitate the proper placement of prosthetic valves during valve repair or replacement surgery by more accurately and easily determining the location of components of the valve assembly with respect to anatomical landmarks.